Advanced loading strategies for corrosion indicators in self-warning anticorrosion coatings: From physical doping to multifunctional integrated systems

The structural safety risks and economic losses caused by metal corrosion have intensified the need for efficient early-warning and protective technologies. Innovative self-warning coatings, integrated with corrosion indicators for visual monitoring of coating damage and metal corrosion, have emerged as a prominent research focus in corrosion protection. This review systematically examines the loading strategies and technological advancements of corrosion indicators in novel anticorrosion coatings, emphasizing the shift from traditional physical doping methods toward multiscale and multifunctional integrated systems. Conventional physical doping approaches are being progressively phased out due to issues such as indicator leakage and low response sensitivity. The emerging loading strategies, such as chemical bonding, microencapsulation, and porous nanocarrier technologies, have achieved efficient and stable indicator incorporation along with precise response characteristics. Future research will concentrate on the development of high-loading, controlled-release biomimetic carriers, and promote the use of environmentally friendly water-based carriers and chromium-free indicators, thereby advancing corrosion protection systems toward greener, smarter, and more sustainable development.